The present invention relates to a solution treatment apparatus for performing the designated treatment after supplying a solution to a substrate.
In a photo-resist process of semiconductor device fabrication, for example, a resist solution is coated on a surface of a substrate such as a semiconductor wafer (referred to as "a wafer" hereinafter) to form a resist film. After the predetermined pattern is exposed, the substrate is developed with a developing solution. A developing unit is used so far in the above developing process.
A developing unit generally includes a rotary stand such as a spin chuck for rotating a wafer while adsorbing and holding it and a developing solution supply nozzle movable to the designated position above the rotary stand. The developing solution supply nozzle has a structure of, as it were, a header with longer length than the diameter of the wafer, and discharge openings disposed in a line on a lower surface thereof. In order to coat a wafer with a developing solution by means of the above developing solution supply nozzle, first, the developing solution supply nozzle is moved to the designated position above the wafer held by the rotary stand, that is, the position just on top of the diameter of the wafer. Next, a developing solution is supplied to the developing solution supply nozzle. While the developing solution is discharged toward the wafer from discharge openings, the wafer makes more than a half rotation so as to uniformly coat the whole surface of the wafer with the developing solution.
Since a developing process is required to perform uniformly, it is desirable that the total time of a discharged developing solution remaining on a wafer is made the same over the whole surface of the wafer as much as possible. Therefore, in order to swiftly coat the whole wafer, discharge pressure is set high and thereafter a developing solution is discharged from discharge openings.
When the discharge pressure of a developing solution is, however, set high as described above, the surrounding air enters into the discharged developing solution, which causes the occurrence of minute bubbles called micro-bubbles in a developing solution film coated on the surface of a wafer. When micro-bubbles occur, only spots of occurrence of micro-bubbles on the surface of the wafer are not developed, and as a result the designated developing process is not performed, thus reducing a yield rate. When a developing solution is discharged at high pressure, impact against a wafer is increased, and there is the possibility that a resist pattern formed by exposure as pretreatment peels off. Especially a resist pattern recently becomes more and more minute, and thus for a minute resist pattern the above possibility is larger.